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Observability & SLOs

observabilitysystem-designmetricstracingslo

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Full lesson · 8 learning steps Open any exercise for focused practice

Step 1 of 8 · intro card

Learn Observability & SLOs

Reliability

Observability lets you understand a running system from its outputs. The three pillars are metrics (RED/USE), structured logs, and distributed traces; SLIs and SLOs define reliability targets with an error budget, and alerting fires on user-facing symptoms.

Observability rests on three pillars. Metrics are cheap numeric time series — the RED method (Rate, Errors, Duration) for request services and USE (Utilization, Saturation, Errors) for resources. Structured logs are searchable key-value records of discrete events.

Distributed traces stitch a single request together as it hops across services, so you can see exactly which hop was slow or failed. Together the pillars answer what is wrong, where, and why.

An SLI is a measured indicator like success rate; an SLO is the target for it, and the gap below 100% is the error budget you may spend on risk. Alert on user-facing symptoms, not every internal blip, so on-call hears signal instead of noise.

Three pillars: metrics, structured logs, distributed traces.

RED = Rate, Errors, Duration per request service.

An SLO sets a target; its gap below 100% is the error budget.

observability:
  metrics: rate-errors-duration
  logs: structured-searchable
  traces: request-across-services
  slo: target-and-error-budget
  alerting: symptom-based

Read the implementation

Connect each part of the code to the concept before you type.

1. Metrics

The RED method tracks Rate, Errors, and Duration per service — the headline numbers for request health.

metrics: rate-errors-duration

2. Logs

Structured (key-value) logs are searchable and filterable, unlike free-text lines.

logs: structured-searchable

3. Traces

Distributed traces follow a single request across services, showing where time and failures occur.

traces: request-across-services

4. SLO

An SLO sets a reliability target; the gap below 100% is the error budget you can spend.

slo: target-and-error-budget

5. Alerting

Alert on user-facing symptoms (slow, failing requests), not every internal blip, to cut noise.

alerting: symptom-based

A complete learning loop

Understand

Read the concept map and follow the code breakdown.

Reconstruct

Type the implementation, repair mistakes and work through every recall exercise.

Verify

Use the final check without hints; revisit weak concepts in short practice sessions.